Elkhorn Slough teeters on 'algal mess'
Marissa Fessenden
Monterey Herald
11/13/2011
Thick, bright green mats of algae carpet corners of Elkhorn Slough.
The growth threatens to choke the home of shorebirds, economically important fish species and ever-popular sea otters. The algae is feeding on a rich flow of nutrients running off from the surrounding land.
A recent paper in Marine Ecology Progress Series by UC Santa Cruz researchers draws a clear map of the problem areas.
Brent Hughes, graduate student in marine ecology and lead author of the paper, said the algae uses oxygen in the water and sediment, making it hard for fish and plants to survive.
Areas of the slough with the worst problem are behind tidal control gates, put in place to prevent tidal water from eroding the surrounding land. Without tidal flow, those areas never get flushed clean and turn into dead zones that threaten life in the estuary.
"It has species that are found nowhere else," said Kerstin Wasson, adjunct associate professor at UCSC and research coordinator at Elkhorn Slough National Estuarine Research Reserve. "There are nurseries for flatfish that support offshore fisheries, and also many part-time residents like migrating shorebirds."
The slough is handling the extremely high nutrient loads now, but it could be steps away from a habitat in trouble.
"We could be teetering on this ecological balance between a somewhat OK, functioning system with eel grass, sea otters and seals and lots of birds," said Hughes, "to one that is not functioning anymore and isjust a soupy algal mess."
The excess nutrients enter the slough mainly from the Salinas River watershed as runoff from fertilized fields. An important step is to stem that fertilizer flow, which is rich in nitrates and feeds the algae.
